1. Field of the Invention
The present invention relates to a display device containing a emitting layer that exhibits the electroluminescence (EL) phenomenon, and a method for manufacturing the display device.
2. Description of the Related Art
Light sources taking advantage of the EL phenomenon have been studied and developed for the purpose of wide range of applications in an illumination device and a backlight of a display as well as for luminescent devices such as luminescent pixels of a display.
The luminous characteristics of the organic EL display device are degraded by oxygen and water. Various methods have been proposed for maintaining the inside of the display device in a dry atmosphere.
One method is to cover the element with a sealing substrate, and to dispose a desiccant on the inner surface of the sealing substrate. However, it is necessary to secure a sufficient space on the inner surface of the substrate in order to dispose the desiccant in a sufficient amount enough for absorbing oxygen and water invading from the outside. In addition, manufacture of the sealing substrate requires cost and time such that a storage space of the desiccant is provided at a part of the sealing substrate. Further, the surface becomes rough due to the desiccant, which may be peeled anywhere. This may cause defective elements by direct contact of the desiccant with the organic EL element.
JP-A 2006-114405 (KOKAI) proposes a method for disposing a desiccant layer around the luminous region on the substrate within the element. However, this is the method not desirable for the display since a region other than the luminous region is added. Oxygen and water having passed through the region in which the desiccant layer is disposed arrive at the luminous region.
Japanese Patent No. 2776040 proposes a method for forming a sealing layer containing the desiccant on the surface of a cathode. Transmittance of the sealing layer decreases by allowing the sealing layer to contain a sufficient amount of the desiccant when the organic EL display device emits the light from the cathode side. Consequently, light emission efficiency of the organic EL display device decreases while electric power consumption increases due to the decrease in luminous efficiency.